Conventional electric motors typically rely on the interaction of magnetic fields provided by electromagnets or permanent magnets. In this regard, the attractive and repulsive forces of such magnetic fields may be used to provide mechanical motion.
However, the magnetic field strength available from conventional electromagnets and permanent magnets grows significantly weaker over very short distances. As a result, the distances between magnets of opposing or attracting magnetic fields in conventional electric motors are generally kept very small in order to provide sufficient magnetic field strength for mechanical applications. For example, typical air gaps for small brushless DC motors may range from about 0.005 to 0.015 inches.
Unfortunately, such requirements can negatively impact the design of electric motors. For example, because of the need to maintain relatively tight tolerances between magnets, conventional electric motors are generally ill-suited for harsh environments where dust or sand may become lodged between, for example, rotor and stator members of the motor.
One approach to increasing magnetic field strength is the use of iron-cored electromagnets. Because iron cores can reinforce the magnetic fields produced by coil windings of electromagnets, greater distances can be provided between magnets. However, such iron cores can significantly increase the weight of electric motors. This increased weight can seriously compromise the usefulness of such motors, especially in environments where weight savings is at a premium such as in electric motors included in space-bound payloads.
Accordingly, there is a need for an improved approach to electric motor design that permits gaps between magnets and inductors to be increased. Moreover, there is a need to provide such gaps without unduly increasing the weight of electric motors.